No longer constrained by the inflexibility of hardwired circuitry, a SDR receiver's functionality can be changed by a software upgrade only. A completely different application can be often implemented using an identical hardware platform, with the functionality defined by the software alone, thus affording a far greater flexibility to the designer than if working with hardware components alone.

Reliability

As hardware parts are replaced with software code (for example, a diode and a capacitor in an AM demodulator would be replaced by a mathematical routine performed on the digitized signal), and software by itself cannot break down, SDR products are generally more reliable than conventional ones.

Consistency and Stability of Parameters

Parameters of hardware components are subject to temperature changes, manufacturing variations and aging, often resulting in performance differences between what should be identical products. However, software always performs the same. This is why SDR products exhibit a far better parameter predictability and performance consistency between units and reduced effects of aging.

Upgradability

Hardware products are hard and expensive to improve and upgrade, and this typically involves changing modules, boards, etc., often requiring for the product to be sent back to the factory. In contrast, SDR products are to a significant degree "future-proof" and can be improved by a simple software upgrade only, with minimum equipment downtime. New features and functions can be added easily. Improvements in software algorithms can also lead towards improved performance or application usability of existing hardware, extending the lifetime of the hardware.

Reusability

Once the signal-processing or user-interface software has been developed and tested, it can be often re-used on other hardware platforms, to create new receivers or entire product families. This reduces the manufacturer's development time and cost.

Reconfigurability

The entire SDR can be often reconfigured, i.e. its functionality and interface completely altered to suit changing user requirements, by a software modification alone, without the need to replace the hardware platform.

Enhanced Functionality

With conventional technology, certain features would be normally very expensive or even unthinkable. SDR technology makes it possible to implement such features easily and at low cost, usually on a standard general-purpose computer platform.

Lower Cost

Due to a reduced number of hardware parts and software reuseability, an SDR is easier and cheaper to manufacture and maintain.

Transceiver design

Picture 1. Block diagram of the transceiver, including the TX/RX switching.

Implementation

Implementation of the transceiver has begun by testing it's core, the phasing modulator/demodulator. The video below, shows the results.

Phasing modulator initial test

After successful testing of the phasing modulator/demodulator, the LNA was implemented. Implementing the LNA is fairly straight forward. The only thing that had to be done, was to make the whole LNA construction as small as possible. The purpose of the LNA is to be mounted in front of the dish, assumming a parabolic front-fed dish. It's physical size should be as small as possible to ensure minimal interference with the RF beam.

Picture 2. LNA view 1

To ensure minimum size, a 3D construction had to be made. Picture above and below show the whole construction. The DC block, the T-adapter and the heatsink are not present. This is just a prototype to show how the different parts of the LNA should be placed.

Picture 3. LNA view 2

Picture 4. LNA view 3

Picture 5. Complete LNA mounted on heatsink

Picture 6. Complete LNA mounted on heatsink

The two pictures above, show the complete LNA mounted on an aluminum piece that is used as a small heatsink. The two LNAs draw 15V at 350mA and the two relays draw 18V at 180mA. I used 24V relays but I found them to operate ok at 18V. Since they drew less current at 18V and since I was reaching the bias-T maximum current, I decided to drive them at 18V instead.